Natural products are important small molecules for studying, treating, and even causing human diseases, and they typically have unique functional groups that are critical for their biological activities. By exploiting the biosynthetic machinery by which these functionalities are synthesized, it is possible to enhance, vary or diminish the biological activities of parent compounds and apply the biosynthetic machinery to new systems for functional group installation. Toward this goal, the chemical logic and enzymatic machinery underlying natural product biosynthesis need to be fully characterized and understood. This project will focus on functional characterization and mechanistical interrogation of enzymes responsible for biosynthesis of unusual pharmacophores of natural products, including terminal alkyne, isonitrile and N-hydroxytriazene. Unique metalloenzymes have been identified important for their biosynthesis, including the membrane-bound di-iron dependent bifunctional desaturase/acetylenase for alkyne generation, the non-heme iron and ?-ketoglutarate dependent oxidase/decarboxylase for isonitrile synthesis, and a didomain enzyme consisting of a C-terminal methionyl-tRNA synthetase-like domain and an N-terminal cupin domain for N-hydroxytriazene formation. The biochemical and mechanistic understanding of these newly discovered enzymes remain poor, warranting an in-depth study in this project. In addition to serving as the warheads of bioactive natural products, these functionalities have distinct chemical and physical properties and are utilized in bio-orthogonal chemical transformations for various chemical biology applications. We will thus further explore the application of their biosynthetic machinery to install these ?clickable? functionalities on various biomolecules on demand. The research strategy is innovative in terms of the choice of novel functionalities and their unique but poorly understood biosynthetic machinery, the multidisciplinary research tools, and the goal-oriented approaches to directly target health-related applications. In particular, we go beyond the enzyme and pathway characterization in the approach design, pursuing applications of these unique enzymes in terms of flexibility to have a positive impact on human well-being. The proposed research is thus significant due to both implications for the field of natural product enzymology and utilities in biomedical and biotechnological research at the basic and translational levels.